Setting Mail Server Inside CentOS VPS
- Install and Test Mail Server
- Configure Authorized Networks
Set Up and Test Mail Server
In the current guide we are going to leverage the Postfix mail server, so follow the next steps to install it within my VPS container and verify if it works as intended.
1. Run the Postfix installer with the following yum command:
2. During the installation process, I’ll need to confirm (i.e. press and submit the ‘y’ response) the following points:
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total download size
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importing GPG key
3. When the installation is finished, I can test mail server operability with the following command:
Here, the {my_email} placeholder is an email address, the test email will be sent to.
4. Now, check the specified email inbox to ensure a letter was sent.
Great! The email server is installed and we can proceed to apply the appropriate configurations.
Configure Postfix Authorized Networks
For the proper workflow of the recently installed Postfix mail server, I may need to apply some settings within its main configuration file. For example, I can manually specify the list of “trusted” clients, that will be able to relay emails through the Postfix:
1. Edit the main.cf file, located in the etc/postfix directory with the following content:
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when Postfix should forward emails only from the local machine, uncomment (remove # at the start of the string) the following line:mynetworks_style = host
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alternatively, I can adjust the list of “trusted” clients manually using the next parameter (in this case the previous setting will be ignored):
mynetworks = {server1 IP address}, {server2 IP address}
2. After editing the configuration files, I need to reload Postfix in order to apply changes I’ve made.
etc/init.d/postfix restart
3. Now I can send messages from the previously specified client (the local machine or the stated server(s)).
However, I also need to adjust my application to work properly with the newly installed mail server. For that, add the code of the following type to my applicatication configuration file deployed to VPS container.
import java.util.Properties;
import javax.mail.Message;
import javax.mail.MessagingException;
import javax.mail.PasswordAuthentication;
import javax.mail.Session;
import javax.mail.Transport;
import javax.mail.internet.InternetAddress;
import javax.mail.internet.MimeMessage;
public class SendMailTLS {
public static void main(String[] args) {
Properties props = new Properties();
props.put("mail.smtp.auth", "false");
props.put("mail.smtp.starttls.enable", "false");
props.put("mail.smtp.host", "host");
props.put("mail.smtp.port", "25");
try {
Session session = Session.getInstance(props);
Message message = new MimeMessage(session);
message.setFrom(new InternetAddress("from-email@jelastic.com"));
message.setRecipients(Message.RecipientType.TO,
InternetAddress.parse("to-email@jelastic.com"));
message.setSubject("Testing Subject");
message.setText("Text of the message");
Transport.send(message);
System.out.println("Done");
} catch (MessagingException e) {
throw new RuntimeException(e);
}
}
}
That’s all. The mail server has been successfully adjusted to work with the application deployed to VPS container.